Billions of miles away, a spacecraft shaped like a grand piano is speeding into the outer solar system carrying a 1991 postage stamp, a piece of SpaceShipOne, and the ashes of Clyde Tombaugh, the astronomer who discovered Pluto. This episode tells the life story of New Horizons, from a 1992 phone call asking Tombaugh for permission to visit his planet, through the political fight that revived a cancelled mission, to the historic flybys of Pluto and Arrokoth.

We explain why the 2006 launch had a 23-day window tied to a Jupiter gravity assist, how a spare Cassini radioisotope thermoelectric generator powers the probe on just a few hundred watts, and the thermal design that keeps it warm near absolute zero. We revisit the safe-mode scare ten days before the Pluto encounter, the 22 hours of planned radio silence during closest approach, and the ...